Abstract

Eoarchean rocks in the Napier Complex of East Antarctica are largely known from a few localities in the western Tula Mountains of Enderby Land. Zircon from trondhjemitic and mafic gneisses from Aker Peaks in Kemp Land, 200 km further east, were analysed by secondary ion mass spectrometry (SIMS), yielding concordant UPb dates between 3860 and 3700 Ma, which can be attributed to magmatic and possibly metamorphic activity. Concurrent analysis of 207Pb/206Pb ratios and LuHf isotopes in the trondhjemitic sample by laser ablation ICPMS provide initial εHf(t) estimates for this age range that are slightly sub-chondritic (ca 0 to −2). This can be attributed to the incorporation of older crust into the magmatic protoliths of the gneisses, although there is no requirement that this crustal source be older than Eoarchean. Much scatter in the UPb dataset is attributable to isotopic disturbance of Pb during high-temperature metamorphism at 2.5 Ga, and if not corrected for, can lead to overestimation of model crust formation ages, a critical problem in the search for evidence of Hadean crust in Eoarchean rocks, and for estimating the timing and rate of ancient continental growth.

Full Text
Paper version not known

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.